1918] SOILS — FERTILIZERS. 325 



[Progress report of soil and fertilizer work in Rhode Island], B. L. Hart- 

 well {Bui. R. 1. State Col., 12 (1911), No. 4, pp. 18-23).— This briefly reviews 

 the progress during 1916 of investigations relating to vegetable matter for the 

 soil, the efficiency of manures, the neutralization of sour soils, and specific plant 

 differences and needs. 



Food from the air, H. Leffmann {Trans. Wagixer Free Inst. Sci. PhUa., 8 

 {1917), pp. 1-14, fiffs- 4)- — This is a description of the processes of fixation of 

 atmospheric nitrogen by oxidation, by absorption, and as ammonia. A biblio- 

 graphy of recent literature on the subject is appended. 



The fixation of nitrog'en in feces, E. H. Richards {Jour. Agr. Sci. [England}, 

 8 (1917), No. 3, pp. 299-311, figs. 2 ) .—Experiments conducted at the Rothamsted 

 Experiment Station with horse and cow manure are reported. 



It was found that " hor.se feces contain material capable of fixing nitrogen 

 when fermented aerobically in presence of sufficient moisture and calcium car- 

 bonate. This fixation is a function of the diet, for when horses are fed on 

 grass alone instead of corn and hay the amount of nitrogen fixed is much re- 

 duced. Under the most favorable conditions 1 gm. of dry matter in the feces 

 will fix 4 mg. of nitrogen. Bullock feces will also fix nitrogen but to a much 

 smaller extent than horse feces. This is also a function of the diet as it only 

 occurs when the animals are fed with cake. On grass alone no nitrogen is fixed. 



" The organisms concerned in the fixation of nitrogen are present in garden 

 soil. Evidence is adduced to shov/ that fixation is brought about by a mixed 

 culture of Azotobacter and Bacillus lactis wrogenes. Of these the latter is 

 normally present in feces ; Azotobacter is not, but readily infects feces. Both 

 organisms are present in the soil used and will fix nitrogen in raw feces but 

 not in sterile feces." 



The availability of phosphoric acid in rock phosphate, G. S. Feaps (Texas 

 Sta. Bui. 212 (1917), pp. 40). — The results of numerous pot experiments to de- 

 termine the percentage of added phosphoric acid recovered in the crops gi'own 

 upon a soil are reported in detail and previous investigations by the author on 

 the subject are reviewed (E. S. R., 23, p. 423; 34, p. 421.) Detailed data are 

 given for recovery of phosphoric acid by crops from acid phosphate and rock 

 phosphate and the effect of manure upon the recovery. 



" The average recovery of phosphoric acid on 25 pot experiments for several 

 crops is 48.2±2.2 per cent. The average recovery in 22 experiments for the first 

 crop is 30.6, compared with 47.3 per cent for all the crops. The average quan- 

 tity of phosphoric acid removed from manure in 22 experiments is 39.2 per cent, 

 compared with 37.9 for acid phosphate in the same series. The manure has 

 probably made some phosphoric acid of the soil available. The average re- 

 covery from acid pho.sphate when used with manure is less than for the acid 

 phosphate used alone, perhaps due to the supply exceeding the needs of the 

 plants in some of the tests. The average recovery of phosphoric acid from rock 

 phosphate in 21 experiments is 9.1±1.1, compared with 43.9±2.3 for acid phos- 

 phate in the same experiment. Thus the phosphoric acid in rock phosphate had 

 about one-fifth the availability of that in acid phosphate in these tests, in which 

 several crops were grown. 



" There are very decided variations in the value of rock phosphate in differ- 

 ent soils. If the first crops grown are considered, and no others, phosphoric 

 acid of acid phosphate has about six times the availability of that in rock phos- 

 phate. In 19 pot experiments the recovery of phosphoric acid from rock phos- 

 phate alone was 9.6±1.3 per cent, and for rock phosphate with manure it was 

 8,6±1.2 per cent after correction for the phosphoric acid removed fropa the ma- 



